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Topic: Stellar spectroscopy


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In the News (Fri 19 Jul 19)

  
  Stellar - Wikipedia, the free encyclopedia
Stellar astronomy is the study of stars and the phenomena exhibited by the various forms/developmental stages of stars.
Stellar dynamics is the branch of astrophysics which describes in a statistical way the collective motions of stars subject to their mutual gravity.
Stellar evolution is the sequence of changes that a star undergoes during its lifetime, the millions or billions of years during which it emits light and heat.
en.wikipedia.org /wiki/Stellar   (488 words)

  
 Astronomical spectroscopy - Wikipedia, the free encyclopedia
Spectroscopy can be used to derive many properties of distant stars and galaxies, such as their chemical composition and also their motion, via the Doppler shift.
Astronomical spectroscopy began with Isaac Newton's initial observations of the light of the sun, dispersed by a prism.
Most stellar spectra share these two dominant features of the sun's spectrum: emission at all wavelengths across the optical spectrum (the continuum) with many discrete absorption lines superimposed on top.
en.wikipedia.org /wiki/Stellar_spectroscopy   (1149 words)

  
 Search Encyclopedia.com
stellar evolution -> Phases of Stellar Evolution Contraction of the Protostar The initial phase of stellar evolution is contraction of the protostar from the interstellar gas, which consists of mostly hydrogen, some helium, and traces of heavier elements.
stellar evolution stellar evolution, life history of a star, beginning with its condensation out of the interstellar gas (see interstellar matter) and ending, sometimes catastrophically, when the star has exhausted its nuclear fuel or can no longer adjust itself to a stable configuration.
stellar populations stellar populations, two broadly contrasting distributions of star types that are characteristic of different parts of a galaxy.
www.encyclopedia.com /searchpool.asp?target=Stellar+Spectroscopy   (492 words)

  
 Stellar spectroscopy   (Site not responding. Last check: 2007-08-19)
The practice of stellar spectroscopy began in the 19th century ; with thework of Von Fraunhofer and, later, with the work of Secchi.
Stellar spectrum can also be used to derive the age of a star in that recently formed starshave a far higher concentration of elements heavier than helium than stars that were formed early in the universe.
Stellar spectroscopy can also be used to derive the motion of the star via Doppler shift and this can provide information about unseen companions such as fl holes and extrasolar planets.
www.therfcc.org /stellar-spectroscopy-48534.html   (410 words)

  
 [No title]   (Site not responding. Last check: 2007-08-19)
Stellar spectroscopy offers a way to classify stars according to their absorption lines; particular absorption lines can be observed only for a certain range of temperatures because only in that range are the involved atomic energy levels populated.
Also occasionally used are the stellar classifications R, N and S. R and N stars are carbon stars (that is, giants) which run parallel to the normal classification system from roughly mid G to late M. These have more recently been remapped into a unified carbon classifier C, with N0 starting at roughly C6.
Since the radius of a giant star is much larger than a dwarf star while their masses are roughly comparable, the gravity and thus the gas density and pressure on the surface of a giant star are much lower than for a dwarf.
www.online-encyclopedia.info /encyclopedia/s/st/stellar_classification.html   (1364 words)

  
 Astronomical spectroscopy
The practice of stellar spectroscopy began in the 19th century; with the work of Von Fraunhofer and, later, with the work of Secchi.
What causes the lines in stellar spectrum remained a mystery until the end of the 19th century and the discovery of quantum mechanics.
Stellar spectrum can also be used to derive the age of a star in that recently formed stars have a far higher concentration of elements heavier than helium than stars that were formed early in the universe.
www.sciencedaily.com /encyclopedia/astronomical_spectroscopy   (479 words)

  
 Spectroscopy Links
Stellar Spectroscopy is a set of four slides from Armagh Observatory that provide a basic, visual introduction.
Stellar Spectroscopy - STARBASE is part of the Surrey Teachers' Astrophysics Resources and provides a concise set of notes with links on stellar spectroscopy.
Spectroscopy of Supernova Remnants Lesson Plan is one of the set of units developed by teachers and NASA educators for years 9-12.
outreach.atnf.csiro.au /education/senior/astrophysics/spectroscopy_links.html   (1329 words)

  
 [No title]
Spectroscopy was a very attractive field of study to the amateur scientists of the 19th century, and no doubt many of the direct vision spectroscopes to be found at antique shows today were used to admire the natural world without necessarily dissecting it.
After the photographic work of Draper was published, he renewed his photography of stellar spectra, using dry plates, and trailed the star along the slit to widen the spectrum instead of a cylindrical lens.
Using a grating ruled by Wanscheff in Berlin, he attempted stellar spectroscopy in 1881, which was probably the first attempt at obtaining the spectra of a star, but it was not successful.
www.europa.com /~telscope/histspec.txt   (5290 words)

  
 Stellar classification -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-08-19)
In astronomy, stellar classification is a classification of ((astronomy) a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior) stars based initially on (Click link for more info and facts about photospheric temperature) photospheric temperature and its associated spectral characteristics, and subsequenly refined in terms of other characteristics.
Stellar temperatures can be classified by using (Click link for more info and facts about Wien's displacement law) Wien's displacement law; but this poses difficulties for distant stars.
It should be noted that while these descriptions of stellar colors are traditional in astronomy, they really describe the light after it has been scattered by the atmosphere.
www.absoluteastronomy.com /encyclopedia/s/st/stellar_classification.htm   (2287 words)

  
 Learn more about Spectroscopy in the online encyclopedia.   (Site not responding. Last check: 2007-08-19)
The recording and studying of spectrum of energy levels in atoms or molecules in the physical sciences is called spectroscopy.
Mossbauer spectroscopy - Measures the absorption of gamma-rays by atoms bound in a solid as a function of gamma-ray energy.
Raman spectroscopy The study of spectra caused by the scattering and change in frequency of light due to the transition between vibrational/rotational energy levels in molecules.
www.onlineencyclopedia.org /s/sp/spectroscopy.html   (381 words)

  
 Spectroscopy   (Site not responding. Last check: 2007-08-19)
The aim of this paper is to briefly explain what is meant by spectroscopy—stellar spectroscopy in particular—and to summarize the results of an actual research project involving the observation and photography of the spectra of two first-magnitude stars, namely, Sirius and Betelgeuse.
Now that we have seen the fundamentals of stellar spectroscopy, I will be describing the kind of instrument that actually makes this possible, and present a few results of what actually can be done even with relatively modest equipment.
Stellar spectroscopy may sometimes be done without a slit, allowing in this case the detection of as much as 75% of the incident light.
www.armandocaussade.com /astronomy/spectroscopy.html   (3192 words)

  
 Search Results for "Stellar ..."   (Site not responding. Last check: 2007-08-19)
stellar evolution, life history of a star, beginning with its condensation out of the interstellar gas (see interstellar matter) and ending, sometimes catastrophically,...
stellar structure, physical properties of a star and the processes taking place within it.
stellar populations, two broadly contrasting distributions of star types that are characteristic of different parts of a galaxy.
bartleby.com /cgi-bin/texis/webinator/sitesearch?query=Stellar+...   (233 words)

  
 Research
Stellar spectroscopy, binary and variable stars, atmospheres and winds of early type stars, and the solar-stellar connection.
Measurement of stellar spectral energy distributions, observations of stellar convection, high resolution stellar spectroscopy, models of stellar atmospheres.
Equilibrium and stability of rotating stellar models, circulation and mixing in stellar interiors.
www.astro.utoronto.ca /Graduate/research.html   (719 words)

  
 Spectra
Stellar spectra were first observed in the middle of the 19th century.
The differences in stellar spectra, at least for main sequence stars, are caused almost entirely by differences in ionization (after all, if sodium is all ionized, the absorptions of neutral sodium will not be present) and the by the way in which the absorption efficiencies change with temperature.
Stellar speeds, however, are usually measured only in tens of kilometers per second, so the changes are not at all visible directly to the eye.
www.astro.uiuc.edu /~kaler/sow/spectra.html   (5826 words)

  
 Untitled Document   (Site not responding. Last check: 2007-08-19)
He studied planetary and stellar spectra with his theodolite telescope and found lines D,E,b and F perfectly defined and he was convinced that the light he observed from Venus included many of the same lines that could be seen in the spectrum of the Sun.
Although the application of spectroscopy to the visual portion of the spectrum dominates the early history of the science of spectroscopy, this invaluable tool has found equally great utility in areas beyond the visible portions of the electromagnetic spectrum.
The progressive evolution of spectroscopy was a direct result of the synthesis of many scientific disciplines, including mathematics, optics, chemistry and physics, culminating in the birth of the new science of astrophysics.
www1.wcf.net /~radduci/Papers/607-p.html   (6035 words)

  
 Georgia State University Astronomy Program - MTT
The primary scientific mission of the MTT is high signal-to-noise stellar spectroscopy at high resolution of bright objects.
Individual stellar spectra are reconstructed from full-phase spectra taken of the binary star system using a locally-developed tomographic analysis algorithm.
Stellar parameters are refined from features of the reconstructed individual spectra.
www.chara.gsu.edu /HLCO/mtt   (313 words)

  
 Sampling and field considerations for PSF fitting photometry
Lets suppose that the stellar profile at the focal plane is sampled by N contiguous hexagonal microlenses.
A practical limitation of the method is evident in the cases where it is not possible to derive a reliable, "noise-free", estimation of the stellar profile.
The direct imaging (or zero order) IFU remapped stellar image would be the counterpart of the stellar profile in the extraction of stellar IFU spectra.
www.pa.msu.edu /soar/SAC/stellarifu.html   (1065 words)

  
 Dainis Dravins (Lund Observatory)
One main topic is analyses of the spectroscopic signatures of stellar surface structure (granulation).
In integrated starlight, stellar granulation manifests itself as slight asymmetries and wavelength shifts of photospheric spectral lines, caused by the unequal photon contributions from hot, rising (thus blueshifted), and cool and sinking (redshifted) surface elements.
Such data of the center-to-limb changes of stellar line profiles, asymmetries and wavelength shifts (and their time changes) will be required to analyze the detailed physics of stellar line formation.
www.astro.lu.se /~dainis/HTML/SPECTROS.html   (585 words)

  
 Yale/Chile Local Group Project
It is not an exaggeration to say that studies of LG galaxies, including the Milky Way, and their stars and star clusters have provided most of the tests of the theory of stellar evolution, and also a large fraction of what is known about the evolution of galaxies.
The interpretive power of the theory of stellar evolution can be applied to sort out, for example, their histories of star formation.
Stellar spectroscopy can reveal details of their chemical evolution.
www.astro.yale.edu /bailyn/localgroup.html   (784 words)

  
 IAAT (Astronomy): Stellar Atmospheres Group - Research Activities
The general context of this work is the stellar evolution, especially the late stages of intermediate mass stars which end their life as white dwarfs.
This requires high quality spectra from ground and space based observatories covering the stellar spectrum form X-rays to the infrared (see also Section Observation) as well as sophisticated computer simulations (see Section Theory) of the interaction between the radiation field with the hot plasma in the outer layers of the star.
Stellar spectra are obtained at ground or space based observatories described in the next section, the calculation of synthetic spectra are shortly described here.
astro.uni-tuebingen.de /groups/stellar   (1122 words)

  
 Second Announcement
Stellar populations are direct tracers of the star formation history, the chemical enrichment and the assembly of galaxies in the Universe.
If we can interpret the observed properties of nearby stellar populations in terms of physical parameters such as age, star formation history, metallicity and dust content, we will be able to elucidate the processes that were important in the formation of the galaxies we see today.
The new constraints are coming from spatially resolved imaging and spectroscopy of stellar populations in nearby galaxies; optical and near-infrared surface brightness fluctuations of galaxies out to the Coma cluster; and imaging and spectroscopy of hundreds of thousands of galaxies in the local Universe.
www.mpa-garching.mpg.de /~stelpops/Announcements/second.html   (556 words)

  
 ipedia.com: Stellar classification Article
Stellar spectroscopy offers a way to classify stars according to their absorption lines; parti...
They are thought to be dying supergiants with their hydrogen layer blown away by hot stellar winds caused by their high temperatures, thereby directly exposing their hot helium core.
The Yerkes spectral classification, also called the MKK system from the authors' initials, is a system of stellar spectral classification introduced in 1943 by William W. Morgan, Phillip C. Keenan and Edith Kellman of Yerkes Observatory.
www.ipedia.com /stellar_classification.html   (1650 words)

  
 SCYON: Paper abstracts   (Site not responding. Last check: 2007-08-19)
We examine the stellar populations of SSCs and their relation to GCs in two nearby prototypical starbursts, the young merger system NGC 4038/39 (the Antennae) and the dwarf irregular galaxy NGC 1569, which are examples of two widely varied environments in which SSCs form.
The Antennae have formed a large SSC population, and its youngest star-forming regions are embedded in a large reservoir of molecular gas and dust.
Near-IR spectroscopy and spectral population synthesis modeling of the few SSCs in NGC 1569 reveals their supergiant-dominated stellar populations and permits measurement of their ages and internal velocity dispersions, which yield stellar masses and constraints on their initial mass functions (IMFs).
obswww.unige.ch /webda/scyon/Gilbert.html   (347 words)

  
 Amateur Spectroscopy
Spectroscopy by definition is the decomposition of electromagnetic radiation (Visible light in this case) into the frequency domain.
Each chemical element emits or absorbs radiation at defined frequencies hence the light source may then be analyzed for it's chemical makeup.With the advent of inexpensive CCD technology such as the Cookbook series of imagers and more recently webcams the amateur now has multiple options for the recording of astronomical spectra.
Both stellar spectra obtained by prisms and detailed solar spectrum studies demonstrate the variety of subjects obtainable without the necessity of expensive spectrographs, optical instrumentation and software.
www.geocities.com /rlaude2000   (553 words)

  
 Bresolin et al.,Stellar Spectroscopy Far Beyond the Local Group   (Site not responding. Last check: 2007-08-19)
We demonstrate the feasibility of quantitative stellar spectroscopy at distances approaching a ten-fold increase over previous investigations by determining chemical composition, stellar parameters, reddening, extinction and wind properties of one of our targets, a supergiant of spectral type A1 Ia located in the outskirts of NGC 3621.
The metallicity (determined from iron group elements) is reduced by a factor of two relative to the sun in qualitative agreement with results from previous abundance studies based on H II region oxygen emission lines.
Comparing stellar wind momentum and absolute V magnitude with galactic and M31 counterparts we confirm the potential of the wind momentum-luminosity relationship as an alternative tool to estimate extragalactic distances.
www.ifa.hawaii.edu /publications/preprints/00preprints/Bresolin_00-44.html   (184 words)

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